When the torque setpoint of the engine varies sharply and the supercharging of the engine aimed at assisting it in meeting the torque setpoint is obtained only using a turbocharger, the response time of the latter, also referred to as “turbo lag” presents problems.
There are various known solutions for overcoming these problems, for example the use of a number of selectively active turbochargers, the use of an electric compressor or even the use of a centrifugal mechanical compressor.
None of these solutions is truly satisfactory in terms of cost, the space taken up, the effectiveness and breadth of the operating range.
Elsewhere, applications WO 2009/014488 and WO 2008/135722 disclose turbocharger compressor drive systems comprising an epicyclic geartrain. In none of these systems does the annulus gear of the geartrain form a flywheel.
There is still a need to have a compressor drive system that allows the compressor to respond rapidly to a variation in torque setpoint, notably in order to provide a satisfactory answer to the problem of turbocharger response time, while at the same time being relatively inexpensive, being efficient, occupying little space, and being usable over an extended range of speeds of the rotary machine.